Respostas metabólicas e de crescimento em juvenis de Danio rerio alimentados com dietas suplementadas com Spirulina platensis

Abstract

Zebrafish (Danio rerio) is an important animal model for biomedical research, because its many advantages, such as genetic similarity to mammals, short generation interval and low storage cost. However, there is little nutritional research with this species and diets that optimize in laboratories have not yet been standardized. From this, the objective of this work was evaluated as metabolic and growth responses in Danio rerio juveniles fed with dietary supplementation of Spirulina platensis in different environments for 77 days. Six isoprotein, isocaloric and isophosphoric diets were formulated, with the inclusion of Spirulina at levels of 0, 2, 4, 6, 8 and 10% (SP0, SP2, SP4, SP6, SP8 e SP10). A total of 300 zebrafish juveniles 50 days post- fertilization were randomly assigned to six groups (diets), each group containing five replicates with 10 replicate animals. At the end, the data were selected for analysis of variance (ANOVA) and as models tested by the Tukey test. A regression analysis was performed for the growth rate data and the treatment level of the treatments. After 77 days of feeding, the animals fed the SP6 diet showed significantly higher values for final weight and specific growth rate when compared to those fed diets containing the other levels of supplementation. The condition factor was significantly higher in SP6 and SP8 diets compared to SP0, weight gain was higher (P<0.05) at 4 to 10% supplementation levels compared to SP0 and furcal length was greater (P<0.05) in SP4 and SP6 treatments in relation to SP2. No significant differences were observed regarding survival. The SP4, SP6, SP8 and SP10 diets decreased triglyceride levels, while total cholesterol levels were not affected. Lipase activity was higher in animals fed SP6 and SP8 diets compared to control and amylase did not show significant differences between treatments. CAT activity was higher (P<0.05) in fish fed SP8 diets compared to SP0 diet. SOD activity was higher (P<0.05) in the group that consumed the SP10 diet compared to the SP0 and SP2 diets. GST activity was higher (P<0.05) in animals fed SP6, SP8 and SP10 diets than in the SP0 group. No significant differences were observed in relation to the leukogram and the evaluation of the frequency in the four stages of maturation of the oocytes. The mean diameter of oocytes in stage I was higher (P<0.05) in the SP2 treatment compared to SP10 and in stage IV the SP4 and SP8 treatments had the highest mean diameters (P<0.05) and SP0 the smallest. From the results obtained, it is concluded that dietary supplementation of Spirulina platensis increases growth parameters, reduces triglyceride levels, increases lipase activity, improves oxidative stress and increases the mean diameter of oocytes without affecting survival, immunological parameters of zebrafish juveniles.